TY - JOUR

T1 - Short time-scale spectral variability in the A0 supergiant HD 92207 and the importance of line profile variations for the interpretation of FORS 2 spectropolarimetric observations

AU - Hubrig, S.

AU - Schöller, M.

AU - Kholtygin, A.F.

PY - 2014

Y1 - 2014

N2 - Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FOcal reducer low dispersion spectrograph (FORS) 2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of the order of a few hundred gauss. Assuming the ideal case of a non-variable star, this discovery has recently been questioned in one work trying to demonstrate the importance of non-photon noise in FORS 2 observations. The assumption of non-variability of HD 92207 can, however, not be held since substantial profile variations of diverse lines on a time-scale of minutes or maybe even a fraction of a minute are detected in FORS 2 spectra. The presence of short-term spectral variability in blue supergiants, which are considered as Type II supernova progenitors, has not been a subject of systematic studies before and is critical for the current theoretical understanding of their physics. Given the detected short-term variability, the question of the presence of a magnetic

AB - Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FOcal reducer low dispersion spectrograph (FORS) 2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of the order of a few hundred gauss. Assuming the ideal case of a non-variable star, this discovery has recently been questioned in one work trying to demonstrate the importance of non-photon noise in FORS 2 observations. The assumption of non-variability of HD 92207 can, however, not be held since substantial profile variations of diverse lines on a time-scale of minutes or maybe even a fraction of a minute are detected in FORS 2 spectra. The presence of short-term spectral variability in blue supergiants, which are considered as Type II supernova progenitors, has not been a subject of systematic studies before and is critical for the current theoretical understanding of their physics. Given the detected short-term variability, the question of the presence of a magnetic

KW - stars: early-type – techniques: polarimetric — stars: individual: HD 92207 – stars: atmospheres — stars: magnetic fields — stars: variables: general

U2 - 10.1093/mnras/stu388

DO - 10.1093/mnras/stu388

M3 - Article

VL - 440

SP - 1779

EP - 1785

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -